/**
 * Copyright 2006 gworks.com.au
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License. (http://www.apache.org/licenses/LICENSE-2.0)
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed 
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for 
 * the specific language governing permissions and limitations under the License.
 *
 * <dhamma-message src="Atisha (11th century Tibetan Buddhist master)">
 *  The greatest achievement is selflessness. The greatest worth is self-mastery.
 *  The greatest quality is seeking to serve others. The greatest precept is continual awareness.
 *  The greatest medicine is the emptiness of everything. The greatest action is not conforming with the worlds ways.
 *  The greatest magic is transmuting the passions. The greatest generosity is non-attachment.
 *  The greatest goodness is a peaceful mind. The greatest patience is humility.
 *  The greatest effort is not concerned with results. The greatest meditation is a mind that lets go.
 *  The greatest wisdom is seeing through appearances. 
 * </dhamma-message>
 * 
 * @author Ashin Wimalajeewa (ash)
 */
package org.javaongems.std.client;

import com.google.gwt.user.client.ui.StackPanel;
import com.google.gwt.user.client.ui.Widget;

public class ListenableStackPanel extends StackPanel {
	static public interface Listener {
		public void onStackOpen(int idx, Widget target);
		public void onStackClose(int idx, Widget target);
	}

	private int lastVisibleIdx = -1;	// b/c StackPanel::visibleStack is private
	private Listener listener;
	
	public void setListener(Listener listener) {
		this.listener = listener;
	}

	public void showStack(int index) {
		int count = getWidgetCount();
	    if ((index >= count) || (index == lastVisibleIdx))
	        return;
		
		if (lastVisibleIdx > -1 && lastVisibleIdx < count) {
			Widget w = getWidget(lastVisibleIdx);
			if (listener != null)
				listener.onStackClose(lastVisibleIdx, w);
		}
		super.showStack(index);
		lastVisibleIdx = index;
		if (listener != null) {
			Widget w = getWidget(lastVisibleIdx);
			listener.onStackOpen(lastVisibleIdx, w);
		}
	}
	
	public int getStackIndex() {
		return lastVisibleIdx;
	}
}
